1. Field of the Invention
The present invention relates to a dental treating apparatus with a hand piece, more specifically, to a dental treating apparatus having an electrical contact with respect to a cutting tool for cutting and enlarging an inner wall of a root canal of a tooth or a holder for holding the cutting tool.
2. Description of the Background Art
As for a dental treating apparatus with a hand piece, a dental hand piece for treating a root canal used for treating a root canal by cutting and enlarging the root canal of a tooth and for measuring a length of the root canal is provided. For example, following patent documents disclose specific examples of the hand piece for treating the dental root canal.
In a dental hand piece for treating a root canal disclosed in U.S. Pat. No. 3,213,480, an installation unit of a head unit to be installed on a hand piece body is configured by a conductive member. Accordingly, by installing the head unit on the hand piece body in the hand piece for treating the dental root canal as disclosed in U.S. Pat. No. 3,213,480, the installation unit of the head unit is electrically connected to a conductive member (such as a driving and transferring mechanism) configuring a root canal length measuring circuit in the hand piece body.
Also, in the dental hand piece for treating the root canal as disclosed in U.S. Pat. No. 3,213,480, the installation unit of the head unit is electrically connected with a tool holding mechanism for mounting the cutting tool on the head unit via a brush mechanism provided in the installation unit of the head unit. Thereby, the dental hand piece for treating the root canal as disclosed in U.S. Pat. No. 3,213,480 can configure one of signal transmitting circuits for measuring a root canal length to the cutting tool (as shown in FIGS. 2 and 3 of U.S. Pat. No. 3,213,480).
Further, in a dental hand piece for treating a root canal as disclosed in U.S. Pat. No. 3,213,539, a terminal pin connected to a lead in a hand piece body, a contact plug, and a contact jack are disposed in a head unit. In the dental hand piece for treating the root canal as disclosed in U.S. Pat. No. 3,213,539, a contact is attached to the contact jack via a contact plate on a lower surface of the head unit. Here, the contact is configured to be rotated in a vertical direction or a horizontal direction, or slid to contact with a cutting tool. Thereby, the dental hand piece for treating the root canal as disclosed in U.S. Pat. No. 3,213,539 can configure one of signal transmitting circuits for measuring a root canal length to the cutting tool.
Moreover, in a dental hand piece for treating a root canal as disclosed in U.S. Pat. No. 4,638,796, a hand piece body is configured by conductive member, and an insulated and coated conductive wire for transmitting a root canal length measurement signal is disposed in a hand piece where a tip end of the conductive wire is bifurcated. Also, in the dental hand piece for treating the root canal as disclosed in U.S. Pat. No. 4,638,796, one of the bifurcated conductive wire is caused to contact with a head unit shaft member (a tool holder) via contact means and the other is connected to a U-shaped elastic wire. The U-shaped elastic wire is configured to contact with a tool installed on the tool holder.
In the dental hand piece for treating the root canal as disclosed in U.S. Pat. No. 3,213,480, a brush mechanism as an electrical contact is provided in the installation unit of the head unit to sandwich a rotation body (a rotor) as the tool holding mechanism such that the hand piece configures one of the signal transmitting circuits to the cutting tool for measuring the root canal length. In the dental hand piece for treating the root canal as disclosed in U.S. Pat. No. 3,213,480, however, there is a problem in that even if connection error occurs between the rotor and the brush mechanism since the brush mechanism wears out due to receiving repeated rotations of the rotor, it cannot be externally determined whether or not the connection error occurs between the rotor and the brush mechanism.
Also, in the dental hand piece for treating the root canal as disclosed in U.S. Pat. No. 3,213,480, when the connection failure occurs between the rotor and the brush mechanism, a display of a measurement result of a root canal length changes or the display blinks on and off in some cases. In the dental hand piece for treating the root canal as disclosed in U.S. Pat. No. 3,213,480, however, even if a failure occurs in the signal transmitting circuit itself for measuring the root canal length, the display of the measurement result of the root canal length changes or the display blinks on and off in some cases in a similar manner. Accordingly, it is difficult to determine whether the connection error occurs between the rotor and the brush mechanism or the failure occurs in the signal transmitting circuit itself for measuring the root canal length from merely the display of the measurement result of the root canal length.
In the dental hand piece for treating the root canal as disclosed in U.S. Pat. No. 3,213,539, since the contact contacts with the cutting tool on the lower surface of the head unit, an electrical contact point between the contact and the cutting tool is externally exposed. Accordingly, in the dental hand piece for treating the root canal as disclosed in U.S. Pat. No. 3,213,539, even if the contact wears out due to receiving the repeated rotations of the cutting tool to cause a connection failure between the contact and the cutting tool, the wear of the contact can be easily determined by viewing an appearance. It should be noted that it is conceivable that there are some cases where the connection failure between the contact and the cutting tool cannot be determined by merely viewing the appearance when a film of an insulator is formed on a surface of the contact to cause a connection failure between the contact and the cutting tool, for example.
In the dental hand piece for treating the root canal as disclosed in U.S. Pat. No. 4,638,796, the contact means connected to the one of the bifurcated conductive wire is configured to contact with the tool holder in the head unit and the U-shaped elastic wire connected to the other of the bifurcated conductive wire is configured to contact with the tool outside the head unit. In the dental hand piece for treating the root canal as disclosed in U.S. Pat. No. 4,638,796, however, there is a problem in that even if connection error occurs between the tool holder and the contact means since the contact means wears out due to receiving repeated rotations of the tool holder, it cannot be externally determined whether or not the connection error occurs between the tool holder and the contact means.